Moving out
You cannot end an assured shorthold tenancy until the end of the fixed term specified in the tenancy agreement, unless the landlord agrees, or a 'break clause' has been included in the agreement to allow the tenancy to be ended under certain circumstances.
You must give the landlord notice of your intention to leave, as stated in the contract. This is usually one month in writing, expiring on the last day of the tenancy agreement.
Once the fixed term (if any) has expired, the tenancy will become a 'periodic tenancy' if you remain in the property and the landlord has not agreed a brand new tenancy with you. In this case you can end the tenancy by serving the landlord with a notice to quit. This should be in writing giving a minimum notice of one month (if the rent is paid monthly) or four weeks ending on a Sunday (if the rent is paid weekly).